Biodegradable resin composition and molded body and production method thereof

ABSTRACT

There is disclosed a biodegradable resin composition containing 100 parts by mass of a biodegradable polyester resin containing not less than 50% by mass of polylactic acid, 0.1 to 10 parts by mass of a layered silicate, 0.1 to 5 parts by mass of a carbodiimide compound and 0.01 to 5 parts by mass of a phosphite organic compound. Alternatively, the biodegradable resin composition contains a phosphite organic compound and at least one additive selected from the group consisting of a hindered phenol compound, a benzotriazole compound, a triazine compound and a hindered amine compound in an amount of 0.01 to 5 parts by mass in total, instead of containing 0.01 to 5 parts by mass of the phosphite organic compound.

TECHNICAL FIELD

The present invention relates to a biodegradable resin compositionhaving excellent color tone, strength and gas barrier property andhaving improved durability under a moisture heat condition, a moldedbody made of the composition, and a production method of thecomposition.

BACKGROUND ART

In recent years, biodegradable resins typified by polylactic acid haveattracted attention from the viewpoint of environmental conservation. Ofthe biodegradable resins, the polylactic acid is highly useful, becausethe polylactic acid has excellent transparency, is one of the mostheat-resistant resins, is less costly due to the mass-producibility fromvegetable-derived materials such as corn and sweet potato, and cancontribute also to reduction of oil materials. However, when a moldedbody is produced by only the biodegradable resin, the molded body hasinsufficient long term storage stability and moisture heat resistance tocause problems such as the reduction of the strength and molecularweight caused by deterioration and the deteriorated appearance caused bythe reduction of the molecular weight. Therefore, the molded body cannotendure applications where the molded body is repeatedly-used andprolonged use.

As a technique for solving this problem, JP-A-2001-261797 discloses thathydrolysis resistance is enhanced by blocking a carboxyl end ofpolylactic acid with a specific carbodiimide compound. As a method forenhancing the other performance of a biodegradable resin,JP-A-2001-49097 discloses that heat stability can be applied by adding aphenol phosphite compound to an aliphatic polyester resin.

As a method for enhancing the other performance of a biodegradableresin, JP-A-2002-338796 discloses that the strength and gas barrierproperty or the like of the biodegradable resin are enhanced by adding alayered silicate organically treated by specific ammonium ions to thebiodegradable resin. JP-A-9-48908 discloses that hindered phenol,organic phosphite and a phosphonite compound are added to athermoplastic polyester resin as a method for suppressing colorationwhen adding a layered silicate to the thermoplastic polyester resin.JP-A-2000-212422 discloses that the appearance and rigidity of athermoplastic polyester resin made of diol and dicarboxylic acid can beenhanced by adding a layered silicate, one of benzophenone,benzotriazole and cyanoacrylate, and a phosphite compound to thethermoplastic polyester resin.

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

However, when the layered silicate is used for the polylactic acidresin, low-molecular weight substances and metal salts of lactic acidare deposited on the surface of the molded body during the long termstorage of the molded body obtained using the resin to cause problemssuch as deteriorated appearance and reduced color tone caused bycoloration by an ionic compound contained in the layered silicate.Unfortunately, the strength is reduced by the long term storage.

Even if the carbodiimide compound of JP-A-2001-261797 is added forpreventing the strength reduction during the long term storage of thepolylactic acid resin containing the layered silicate, the coloration ofthe polylactic acid resin is insufficiently suppressed in the presenceof the layered silicate, and the effect for improving the strengthreduction is also insufficient. Also, the generation of the depositedsubstance on the surface of the molded body during the prolonged storagecannot be suppressed.

Even if the phenol phosphite, the hindered phenol compound or thephosphonite compound and the like is applied to the polylactic acid asdescribed in JP-A-2001-49097 and JP-A-9-48908, the problems such as thestrength reduction and the deposited substances during the long termstorage are not solved although the effect for improving the color toneis observed in some compounds.

Even if benzophenone, benzotriazole or cyanoacrylate, and the phosphitecompound are added in the system containing the layered silicate asdescribed in JP-A-2000-212422, the appearance is insufficientlyimproved, and the moisture heat resistance is unsuitable for practicaluse. In addition, JP-A-2000-212422 does not refer the polylactic acidwhich is a biodegradability polyester.

To solve the aforesaid problems, it is an object of the presentinvention to provide a biodegradable resin composition having excellentcolor tone, strength and gas barrier property and suppressing thestrength reduction and the generation of deposited substances under amoisture heat condition.

Means for Solving Problem

As the results of the intensive studies for solving the problems, thepresent inventors have found that the initial color tone is improved byadding a carbodiimide compound and phosphite organic compound of aspecified amount with a layered silicate to a biodegradable polyesterresin consisting mainly of polylactic acid, and the strength reductionand the generation of deposited substances in high temperature and highhumidity are suppressed, and attained the present invention.

The characteristic of the present invention is as follows.

(1) A biodegradable resin composition comprises:

100 parts by mass of a biodegradable polyester resin containing not lessthan 50% by mass of polylactic acid;

0.1 to 5 parts by mass of a carbodiimide compound;

0.1 to 10 parts by mass of a layered silicate; and

0.01 to 5 parts by mass of a phosphite organic compound.

(2) The biodegradable resin composition according to the item (1)comprises the phosphite organic compound and at least one additiveselected from the group consisting of a hindered phenol compound, abenzotriazole compound, a triazine compound and a hindered aminecompound in an amount of 0.01 to 5 parts by mass in total, instead ofcontaining 0.01 to 5 parts by mass of the phosphite organic compound.

(3) The biodegradable resin composition according to the item (1) or(2), wherein the biodegradable resin composition has astrength-retaining rate of not less than 60% when being held at 60° C.and at a relative humidity of 95% for 300 hours.

(4) The biodegradable resin composition according to any of the items(1) to (3), wherein the biodegradable resin composition has a YI valueof not more than 25 when the resin composition is measured by acolorimeter.

(5) The biodegradable resin composition according to any of the items(1) to (4), wherein the layered silicate contains primary, secondary,tertiary or quaternary ammonium ions, pyridinium ions, imidazolium ionsor phosphonium ions ionically bonded between layers thereof.

(6) A molded body comprises the biodegradable resin compositionaccording to any of the items (1) to (5).

(7) A method for producing a biodegradable resin composition comprises:

adding a layered silicate when melt-mixing the biodegradable resincomposition or when polymerizing a biodegradable polyester resin, inproducing the biodegradable resin composition according to any of theitems (1) to (5).

(8) A method for producing a biodegradable resin composition comprises:

adding a carbodiimide compound and a phosphite compound when melt-mixingthe biodegradable resin composition or when polymerizing a biodegradablepolyester resin, in producing the biodegradable resin compositionaccording to any of the items (1) to (5).

EFFECT OF THE INVENTION

The present invention can provide a biodegradable resin compositionhaving excellent color tone, strength and gas barrier property,maintaining strength and molecular weight for a long period of time evenin high temperature and high humidity, and suppressing the generation ofdeposited substances such as low-molecular weight substances and metalsalts of polylactic acid. This resin composition can be used for varioustypes of molded bodies, and can be well used for various applications.The resin composition of the present invention, which hasbiodegradability, can be composted when being discarded. Therefore, theresin composition can be reused as a fertilizer, and the amount ofgarbage can be reduced. The polylactic acid, which is generally producedfrom raw materials derived from corn and sweet potato or the like, cancontribute to the prevention of depletion of petroleum resources.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail.

A biodegradable polyester resin of a biodegradable resin composition ofthe present invention should contain not less than 50% by mass ofpolylactic acid. The proportion of the polylactic acid is preferably notless than 60% by mass, more preferably not less than 80% by mass. If theproportion of the biodegradable resin other than the polylactic acid ismore than 50% by mass, the resulting biodegradable resin composition isinferior in mechanical strength, transparency and heat resistance. Rawmaterials derived from vegetable are preferably used for the polylacticacid since petroleum resources are reducibly used.

Examples of the polylactic acids employed as a major component of thebiodegradable polyester resin include poly(L-,lactic acid),poly(D-lactic acid), or a mixture or copolymer of poly(L-lactic acid)and poly(D-lactic acid). The polylactic acid is produced by employing aknown melt polymerization method optionally along with a solid-phasepolymerization method if needed.

Examples of the biodegradable resins which can be used for the presentinvention and are other than the polylactic acid include aliphaticpolyesters such as poly(ethylene succinate), poly(butylene succinate)and poly(butylene succinate-co-butylene adipate) which are each preparedfrom a diol and a dicarboxylic acid; polyhydroxycarboxylic acids such aspolyglycolic acid, poly(3-hydroxybutyric acid), poly(3-hydroxyvalericacid) and poly(3-hydroxycaproic acid); poly(ω-hydroxyalkanoate) such aspoly(ε-caprolactone) and poly(δ-valerolactone); and poly(butylenesuccinate-co-butylene terephthalate) and poly(butyleneadipate-co-butylene terephthalate) which each contain an aromaticcomponent but yet have biodegradability. Other examples includepolyester amides, polyester carbonates, and polysaccharides such asstarch. These components may be used either alone or in combination, andmay be copolymerized. The components may be merely mixed to thepolylactic acid which is the major component, and may be copolymerized.

In the present invention, the biodegradable resin composition contains acarbodiimide compound for applying long-term moisture heat resistanceand appearance stability to the biodegradable resin composition.

Specific examples of the carbodiimide compounds used in the presentinvention include

-   N,N′-di-2,6-diisopropylphenylcarbodiimide,-   N,N′-di-o-tolylcarbodiimide,-   N,N′-diphenylcarbodiimide,-   N,N′-dioctyldesylcarbodiimide,-   N,N′-di-2,6-dimethylphenylcarbodiimide,-   N-tolyl-N′-cyclohexylcarbodiimide,-   N,N′-di-2,6-di-tert-butylphenylcarbodiimide,-   N-triyl-N′-phenylcarbodiimide,-   N,N′-di-p-nitrophenylcarbodiimide,-   N,N′-di-p-aminophenylcarbodiimide,-   N,N′-di-p-hydroxyphenylcarbodiimide,-   N,N′-di-cyclohexylcarbodiimide,-   N,N′-di-p-tolylcarbodiimide,-   p-phenylene-bis-di-o-tolylcarbodiimide,-   p-phenylene-bis-dicyclohexylcarbodiimide,-   hexamethylene-bis-dicyclohexylcarbodiimide,-   ethylene-bis-diphenylcarbodiimide,-   N,N′-benzylcarbodiimide,-   N-octadecyl-N′-phenylcarbodiimide,-   N-benzyl-N′-phenylcarbodiimide,-   N-octadecyl-N′-tolylcarbodiimide,-   N-cyclohexyl-N′-tolylcarbodiimide,-   N-phenyl-N′-tolylcarbodiimide,-   N-benzyl-N′-tolylcarbodiimide,-   N,N′-di-o-ethylphenylcarbodiimide,-   N,N′-di-p-ethylphenylcarbodiimide,-   N,N′-di-o-isopropylphenylcarbodiimide,-   N,N′-di-p-isopropylphenylcarbodiimide,-   N,N′-di-o-isobutylphenylcarbodiimide,-   N,N′-di-p-isobutylphenylcarbodiimide,-   N,N′-di-2,6-diethylphenylcarbodiimide,-   N,N′-di-2-ethyl-6-isopropylphenylcarbodiimide,-   N,N′-di-2-isobutyl-6-isopropylphenylcarbodiimide,-   N,N′-di-2,4,6-trimethylphenylcarbodiimide,-   N,N′-di-2,4,6-triisopropylphenylcarbodiimide,-   N,N′-di-2,4,6-triisobutylphenylcarbodiimide,-   diisopropylcarbodiimide,-   dimethylcarbodiimide,-   diisobutylcarbodiimide,-   dioctylcarbodiimide,-   t-butylisopropylcarbodiimide,-   di-β-naphthylcarbodiimide,-   di-t-butylcarbodiimide, and-   aromatic polycarbodiimide (for example, trade name: Stabaksol I    manufactured by SUMIKA BAYER URETHANE CO., LTD.). These carbodiimide    compounds may be used alone. However, the carbodiimide compounds may    be used in combination. In the present invention,    N,N′-di-2,6-diisopropylphenylcarbodiimide having a high hydrolysis    inhibiting effect is particularly preferable.

The proportion of the carbodiimide compound should be 0.1 to 5 parts bymass based on 100 parts by mass of the biodegradable polyester resin,and preferably 0.5 to 3 parts by mass. If the proportion is less than0.1 part by mass, it is impossible to obtain long-term moisture heatresistance and appearance stability intended by the present invention.Even if the proportion is more than 5 parts by mass, a higher effect isnot observed.

In the present invention, the biodegradable resin composition containsthe layered silicate in order to enhance the strength and gas barrierproperty or the like of the biodegradable resin composition. The layeredsilicate is one type of a swellable lamellar clay mineral, and specificexamples thereof include smectite, vermiculite and swellable fluoromica.Examples of the smectite include montmorillonite, beidellite, hectoriteand saponite. Examples of the swellable fluoromica include Na-typetetrasilicic fluoromica, Na-type taeniolite and Li-type taeniolite.Other usable examples include layered silicates such as canemite,macatite, magadiite and kenyaite which contain neither aluminum normagnesium. A natural layered silicate can be preferably employed as thelayered silicate. Besides the natural layered silicates, a syntheticlayered silicate may be employed. The synthetic layered silicate may beprepared by any of a melt process, an intercalation process and ahydrothermal process. Any of these layered silicates may be used alone.Layered silicates of different types, different production sites anddifferent particle diameters may be used in combination.

For enhancing the dispersibility of the layered silicate in thebiodegradable polyester resin which is the major component of thebiodegradable resin composition of the present invention to enhance thegas barrier property, it is preferable that primary, secondary, tertiaryor quaternary ammonium ions, pyridinium ions, imidazolium ions orphosphonium ions are ionically bonded between layers of the layeredsilicate. The primary, secondary and tertiary ammonium ions are preparedby protonating primary, secondary and tertiary amines correspondingthereto. Examples of the primary amines include octylamine, dodecylamineand octadecylamine. Examples of the secondary amines includedioctylamine, methyloctadecylamine and dioctadecylamine. Examples of thetertiary amines include trioctylamine, dimethyldodecylamine anddidodecylmonomethylamine. Examples of the quaternary ammonium ionsinclude dihydroxyethylmethyloctadecylammonium,dihydroxyethylmethyldodecylammonium, tetraethylammonium,octadecyltrimethylammonium, dimethyldioctadecylammonium,hydroxyethyldimethyloctadecylammonium,hydroxyethyldimethyldodecylammonium,benzyldihydroxyethyldodecylammonium,benzyldihydroxyethyloctadecylammonium,methyldodecylbis(polyethyleneglycol)ammonium, andmethyldiethyl(polypropylene glycol)ammonium. Examples of the phosphoniumions include tetraethylphosphonium, tetrabutylphosphonium,hexadecyltributylphosphonium, tetrakis(hydroxylmethyl)phosphonium and2-hydroxyethyltriphenylphosphonium. Of these, a layered silicate treatedwith ammonium ions or phosphonium ions such asdihydroxyethylmethyloctadecylammonium,dihydroxyethylmethyldodecylammonium,hydroxyethyldimethyloctadecylammonium,hydroxyethyldimethyldodecylammonium,methyldodecylbis(polyethyleneglycol)ammonium,methyldiethyl(polypropyleneglycol)ammonium and2-hydroxyethyltriphenylphosphonium having at least one hydroxyl group inits molecule is particularly preferable because of the strong affinityfor the biodegradable polyester resin and the improved dispersibility.Any of these ionic compounds may be used either alone or in combination.

A method for treating the layered silicate with the primary, secondary,tertiary or quarternary ammonium ions or the phosphonium ions is notparticularly limited. For example, inorganic ions between the layers ofthe layered silicate are first ion-exchanged with ammonium ions orphosphonium ions by dispersing the layered silicate in water or alcohol,adding the primary, secondary or tertiary amines and an acid(hydrochloric acid or the like), a quarternary ammonium salt, or aphosphonium salt and stirring the resulting mixture. Then, the resultingproduct is filtered, rinsed and dried.

The proportion of the layered silicate should be 0.1 to 10 parts by massbased on 100 parts by mass of the biodegradable polyester resin,preferably 0.5 to 8 parts by mass, and more preferably 2 to 5 parts bymass. If the proportion is less than 0.1 part by mass, it is impossibleto obtain the enhanced effect of heat resistance and gas barrierproperty intended by the present invention. If the proportion is morethan 10 parts by mass, the moisture heat resistance and moldability ofthe biodegradable polyester resin tend to be reduced.

In the present invention, this biodegradable resin composition containsa phosphite organic compound for suppressing the coloration of thebiodegradable resin composition and applying heat resistance andmoisture heat resistance to the biodegradable resin composition. Herein,examples of the phosphite organic compounds includetris(2,4-di-tert-butylphenyl)phosphite (trade name: IRGAFOS168manufactured by Ciba Speciality Chemicals, Inc.),bis(2,4-di-tert-butylphenyl)pentaerythritoldiphosphite (trade name:IRGAFOS12 manufactured by Ciba Speciality Chemicals, Inc.),bis[2,4-bis(1,1-dimethylethyl)-6-methylphenyl]ethyl ester phosphite(trade name: IRGAFOS38 manufactured by Ciba Speciality Chemicals, Inc.),tetrakis(2,4-di-tert-butylphenyl)[1,1-biphenyl]4,4′-diylbisphosphonite(trade name: IRGAFOS P-EPQ manufactured by Ciba Speciality Chemicals,Inc.),3,9-bis(p-nonylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5,5]undecane(trade name: Adeka Stub PEP-4C manufactured by ASAHI DENKA CO., LTD.),O,O′-dialkyl(C=8 to 18)pentaerythritoldiphosphite (trade name: AdekaStub PEP-8, PEP-8W manufactured by ASAHI DENKA CO., LTD.),bis(2,4-di-tert-butylphenyl)pentaerythritoldiphosphite (trade name:Adeka Stub PEP24G manufactured by ASAHI DENKA CO., LTD.),bis(2,6-di-tort-butyl-4-methylphenyl)pentaerythritol-di-phosphite (tradename: Adeka Stub PEP36 and PEP-36Z manufactured by ASAHI DENKA CO.,LTD.), 2,2′-methylenebis(4,6-di-tert-butylphenyl)-2-ethylhexylphosphite(trade name: Adeka Stub HP-10 manufactured by ASAHI DENKA CO., LTD.),tris(2,4-di-tert-butylphenylphosphite) (trade name: Adeka Stub 2112manufactured by ASAHI DENKA CO., LTD.),4,4′-butylidene-bis(6-tert-butyl-3-methylphenyl-ditridecylphosphite)(trade name: Adeka Stub 260 manufactured by ASAHI DENKA CO., LTD.),hexaalkyl or [trialkyl(C=8 to18)tris(alkyl(C=8,9)phenyl)]1,1,3-tris(3-t-butyl-6-methyl-4-oxyphenyl)-3-methylpropanetriphosphite(trade name: Adeka Stub 522A manufactured by ASAHI DENKA CO., LTD.), dior mono(dinonylphenyl)mono or di(p-nonylphenyl)phosphite (trade name:Adeka Stub 329K manufactured by ASAHI DENKA CO., LTD.),trisnonylphenylphosphite (trade name: Adeka Stub 1178 manufactured byASAHI DENKA CO., LTD.),(1-methylethylidene)-di-4,1-phenylene-tetra-C12-15-alkylphosphite (tradename: Adeka Stub 1500 manufactured by ASAHI DENKA CO., LTD.),2-ethylhexyl-diphenylphosphite (trade name: Adeka Stub C manufactured byASAHI DENKA CO., LTD.), diphenylisodecylphosphite (trade name: AdekaStub 135A manufactured by ASAHI DENKA CO., LTD.), triisodecylphosphite(trade name: Adeka Stub 3010 manufactured by ASAHI DENKA CO., LTD.),triphenylphosphite (trade name: TPP manufactured by ASAHI DENKA CO.,LTD.), and hydrogenated bisphenol A·pentaerythritolphosphite polymer(trade name: JPH3800 manufactured by JOHOKU CHEMICAL CO., LTD.).

Of these, pentaerythritol diphosphite (PEP 24G),bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol-di-phosphite(PEP36, PEP-36Z), tris(2,4-di-tert-butylphenylphosphite)(2112),hydrogenated bisphenol A·pentaerythritol phosphite polymer (JPH3800) orthe like are more preferable. These may be used either alone or incombination.

The proportion of the phosphite organic compound should be 0.01 to 5parts by mass based on 100 parts by mass of the biodegradable polyesterresin, and preferably 0.05 to 2 parts by mass. If the proportion is lessthan 0.01 part by mass, it is impossible to obtain the suppression ofcoloration, the heat resistance and the moisture heat resistance, whichare intended by the present invention. If the proportion is more than 5parts by mass, the physical properties of the resin composition arereduced by the decomposition of the phosphite organic compound.

The resin composition of the present invention can contain the phosphiteorganic compound, as well as at least one additive selected from thegroup consisting of a hindered phenol compound, a benzotriazolecompound, a triazine compound and a hindered amine compound. Since thisadditive can provide the same effect as that of the case where thephosphite organic compound is used alone, the additive is useful whenthe content of the phosphite compound is limited by restriction or thelike. In using this additive, the total proportion of the additive andphosphite organic compound should be 0.01 to 5 parts by mass based on100 parts by mass of the biodegradable polyester resin, and preferably0.05 to 2 parts by mass. If the proportion is less than 0.01 part bymass, it is impossible to obtain the suppression of coloration, the heatresistance and the moisture heat resistance, which are intended by thepresent invention. If the proportion is more than 5 parts by mass, thephysical properties are reduced and the coloration is caused by thesecompounds and decomposed substances.

Examples of the hindered phenol compounds in the present inventionincludepentaerythritoltetrakis[3-(3,5-di-tert-butyl-hydroxyphenyl)propionate](trade name: IRGANOX 1010 manufactured by Ciba Speciality Chemicals,Inc.),thiodiethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate](trade name: IRGANOX 1035 manufactured by Ciba Speciality Chemicals,Inc.), octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (tradename: IRGANOX 1076 manufactured by Ciba Speciality Chemicals, Inc.),N,N′-hexane-1,6-diylbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide](trade name: IRGANOX 1098 manufactured by Ciba Speciality Chemicals,Inc.), benzene propanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy,C7-C9 side-chain alkylester (trade name: IRGANOX 1135 manufactured byCiba Speciality Chemicals, Inc.),2,4-dimethyl-6-(1-methylpentadecyl)phenol (trade name: IRGANOX 1141manufactured by Ciba Speciality Chemicals, Inc.),diethyl[{3,5-bis(1,1-dimethylethyl)-4-hidoroxyphenyl}methyl]phosphonate(trade name: IRGANOX 1222 manufactured by Ciba Speciality Chemicals,Inc.),3,3′,3″,5,5′,5″-hexa-tert-butyl-a,a′,a″-(mesitylene-2,4,6-triyl)tri-p-cresol(trade name: IRGANOX 1330 manufactured by Ciba Speciality Chemicals,Inc.), a mixture (trade name: IRGANOX 1425WL manufactured by CibaSpeciality Chemicals, Inc.) of calciumdiethylbis[[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate]and polyethylene wax, 4,6-bis(octylthiomethyl)-o-cresol (trade name:IRGANOX 1520L manufactured by Ciba Speciality Chemicals, Inc.),ethylenebis(oxyethylene)bis[3-(tert-buyl-4-hydroxy-m-tolyl)propionate](trade name: IRGANOX 245 manufactured by Ciba Speciality Chemicals,Inc.), 1,6-hexanediol-bis[3(3,5-di-t-butyl-4-hydroxyphenyl)propionate](trade name: IRGANOX 259 manufactured by Ciba Speciality Chemicals,Inc.), 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanuric acid(trade name: IRGANOX 3114 manufactured by Ciba Speciality Chemicals,Inc.),1,3,5-tris[(4-tert-butyl-3-hydroxy-2,6-xylyl)methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione(trade name: IRGANOX 3790 manufactured by Ciba Speciality Chemicals,Inc.), a reaction product (trade name: IRGANOX 5057 manufactured by CibaSpeciality Chemicals, Inc.) of N-phenylbenzenamine and2,4,4-trimethylpentene,6-(4-hydroxy-3,5-di-t-butylanilino)-2,4-bisoctylthio-1,3,5-triazine(trade name: IRGANOX 565 manufactured by Ciba Speciality Chemicals,Inc.), 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanuric acid(trade name: Adeka Stub AO-20 manufactured by ASAHI DENKA CO., LTD.),1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane (trade name:Adeka Stub AO-30 manufactured by ASAHI DENKA CO., LTD.),4,4′-butylidenebis(6-tert-butyl-3-methylphenol) trade name: Adeka StubAO-40 manufactured by ASAHI DENKA CO., LTD.),3-(4′-hydroxy-3′,5′-di-tert-butylphenyl)propionic acid-n-octadecyl(trade name: Adeka Stub AO-50 manufactured by ASAHI DENKA CO., LTD.),pentaerythritoltetrakis[3-(3′,5′-di-tert-butyl-4′-hydroxyphenyl)propionate](trade name: Adeka Stub AO-60 manufactured by ASAHI DENKA CO., LTD.),triethyleneglycolbis[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionate](trade name: Adeka Stub AO-70 manufactured by ASAHI DENKA CO., LTD.),3,9-bis[1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenylpropionyloxy)ethyl]2,4,8,10-tetraoxspiro[5,5]-undecane(trade name: Adeka Stub AO-80 manufactured by ASAHI DENKA CO., LTD.),1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene(trade name: Adeka Stub AO-330 manufactured by ASAHI DENKA CO., LTD.),and 2,2-oxamidebis-[ethyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate](trade name: Naugard XL-1 manufactured by Crompton-Uniroyal Chemical).

Of these, particularly,pentaerythritoltetrakis[3-(3,5-di-tert-butyl-hydroxyphenyl)propionate](IRGANOX 1010),1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene(AO-330) or the like are preferably used. These may be used either aloneor in combination.

Examples of the benzotriazole compounds include2-(2′-hydroxy-5′-methylphenyl)benzotriazole (trade name: TINUVIN Pmanufactured by Ciba Speciality Chemicals, Inc.),2-(2H-benzotriazole-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (tradename: TINUVIN234 manufactured by Ciba Speciality Chemicals, Inc.), and2-(2′-hydroxy-3′-t-butyl-5′-methylphenyl)-5-chlorobenzotriazole (tradename: TINUVIN326 manufactured by Ciba Speciality Chemicals, Inc.).

Examples of the triazine compounds include2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-[(hexyl)oxy]-phenol (trade name:TINUVIN1577FF manufactured by Ciba Speciality Chemicals, Inc.), and2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl]-5-(octyloxy)phenol(trade name: UV-1164 manufactured by Cytec Industries).

Examples of the hindered amine compounds includepoly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)imino}](trade name: CHIMASSORB944FDL manufactured by Ciba Speciality Chemicals,Inc.).

It is preferable that the biodegradable resin composition of the presentinvention has a strength-retaining rate of not less than 60% when 300hours pass at 60° C. and at a relative humidity of 95%. Herein, thestrength-retaining rate is prepared by producing a test piece using aresin composition, measuring the test piece based on ASTM-D790, andcalculating the retaining rate of the flexural strength before and afterbeing treated.

The resin composition of the present invention has excellent color tone,and preferably, the resin composition has a YI value of not more than25. If the YI value is more than this value, the commercial value, forexample, of a molded body molded by the resin composition is reduced.Herein, the YI value means yellowness calculated from three tristimulusvalues. The larger the YI value is, the more intensive the yellownessis, and the smaller the YI value is, the weaker the yellowness is.

Examples of methods for adding a carbodiimide compound, a phosphiteorganic compound and the above additive in producing the biodegradablepolyester resin of the present invention include a method formelt-kneading the biodegradable polyester resin, the carbodiimidecompound, the phosphite organic compound and the additive using anordinary kneader, and a method for polymerizing a monomer of thebiodegradable polyester in the presence of a predetermined amount of thecarbodiimide compound, phosphite organic compound and additive withrespect to the monomer to provide the biodegradable polyester resincomposition. Of these, the former method is preferable because of lessreduction of the molecular weight of the biodegradable polyester resinand simple addition or the like.

Examples of the methods for adding the layered silicate in producing thebiodegradable resin composition of the present invention include amethod for adding the layered silicate when polymerizing thebiodegradable polyester resin, a method for adding the layered silicatewhen melt-kneading the biodegradable polyester resin, and a method foradding the layered silicate when molding a molded body. Of these, it ispreferable to add the layered silicate when melt-kneading thebiodegradable polyester resin or molding the molded body. Examples ofthe methods for adding the layered silicate when melt-kneading thebiodegradable polyester resin and when molding the molded body include amethod for previously dry-blending a resin and a layered silicate andsupplying the blended mixture to an ordinary kneader or an injectionmolding machine, and a method for adding the layered silicate duringkneading using a side feeder.

In melt-kneading the biodegradable polyester resin, an ordinary extrudersuch as a single screw extruder, a twin screw extruder, a roll kneaderand Brabender can be used. The use of the twin screw extruder ispreferable for improving the dispersibilities of the layered silicate,carbodiimide compound, phosphite organic compound and additive.

Magnesium stearate, a phosphate ester surface-active agent, and apartially saponified ester of a montanic acid or the like may be addedto the biodegradable polyester resin for improving the dispersibility ofthe layered silicate. For improving this dispersibility, a resin may bedenatured with anhydrous maleic acid or the like and a polar group maybe introduced.

A heat stabilizer, an oxidation inhibitor, a pigment, a weather-proofagent, a flame retarder, a plasticizer, a lubricant, a release agent, anantistatic agent, a filler and a dispersant or the like other than thespecified ones in present invention may be added to the resincomposition of the present invention, as long as the effect of thepresent invention is not damaged by the addition. Examples of the heatstabilizer and the oxidation inhibitor include sulfur compounds, coppercompounds and halides of alkali metals, which may be used as a mixture.These additives are generally added in melt-kneading or polymerizing.Exemplary inorganic fillers among the fillers include talc, calciumcarbonate, zinc carbonate, walastonite, silica, alumina, magnesiumoxide, calcium silicate, sodium aluminate, calcium aluminate, sodiumaluminosilicate, magnesium silicate, glass balloon, carbon black, zincoxide, antimony trioxide, zeolite, hydrotalcite, metal fibers, metalwhisker, ceramic whisker, potassium titanate, boron nitride, graphite,glass fibers and carbon fibers. Exemplary organic fillers among thefillers include naturally occurring polymers such as starch, celluloseparticles, wood powder, bean curd lees, chaff, bran and kenaf anddenatured materials thereof.

To the biodegradable resin composition of the present invention, anon-biodegradable resin such as polyamide (nylon), polyethylene,polypropylene, polybutadiene, polystyrene, an AS resin, an ABS resin,polyacrylic acid, polyacrylic acid ester, polymethacrylic acid,polymethacrylic acid ester, polyethylene terephthalate,polyethylenenaphthalate, polycarbonate and a copolymer thereof may beadded as long as the effect of the present invention is not damaged.

The resin composition of the present invention can be used as variousmolded bodies by known molding processes such as injection molding, blowmolding and extrusion molding.

For the injection molding process, it is possible to employ an ordinaryinjection molding process, a gas injection molding process and aninjection press molding method. A cylinder temperature in the injectionmolding process, that is, the molding temperature should be not lessthan the melting point (Tm) or fluidization temperature of polylacticacid, is preferably 180 to 230° C., and more preferably 190 to 220° C.If the molding temperature is too low, the flowability of the resin isreduced to cause poor molding or overloading of a molding apparatus.Conversely, if the molding temperature is too high, the polylactic acidis decomposed, so that the resulting molded body disadvantageously has areduced strength or is colored. On the other hand, the mold temperatureis preferably not more than Tg−10° C. when the mold temperature is notmore than the glass transition temperature Tg of the resin composition.The mold temperature may not be less than Tg and can not be more thanTm−30° C. for accelerating the crystallization for improvement of therigidity and heat resistance of the molded body.

For the blow molding process, it is possible to employ a direct blowingmethod in which material chips are directly molded, an injection blowmolding method in which a preform (bottomed parison) is firstinjection-molded and then blow-molded, and a stretch blow moldingmethod. For the injection blow molding method, it is also possible toemploy a hot parison method in which a preform is blow-moldedimmediately after formation of the preform, or a cold parison method inwhich a preform is once cooled and unmolded and then heated again to beblow-molded.

As the extrusion process, a T-die technique and a circular die techniqueor the like may be employed. The extrusion temperature should be notless than the melting point (Tm) or fluidization temperature of thepolylactic acid as the raw material. The extrusion temperature ispreferably in the range of 180 to 230° C., more preferably 190 to 220°C. If the extrusion temperature is too low, the operation isunstabilized or overloaded. Conversely, if the extrusion temperature istoo high, the polylactic acid is decomposed, so that theextrusion-molded body disadvantageously has a reduced strength or iscolored. A sheet or a pipe or the like can be produced by extrusionmolding.

Specifically, the sheet or pipe prepared by the extrusion process, maybe used as a material sheet for deep drawing, a material sheet for batchfoaming, cards such as credit cards, desk pads, clear files, straws, andagricultural/horticultural rigid pipes or the like. A food container, anagricultural/horticultural container, a blister package and apress-through package or the like may be produced by a deep drawingprocess by vacuum-forming, air-pressure-forming orvacuum-air-pressure-forming the sheet. The deep-drawing temperature andthe heat treatment temperature are preferably Tg+20° C. to Tg+100° C. Ifthe deep drawing temperature is less than Tg+20° C., the deep drawing isdifficult. Conversely, if the deep drawing temperature is more thanTg+100° C., the polylactic acid is decomposed; the resulting containerhas an uneven wall thickness and an uneven orientation thereby to have areduced impact resistance. The shapes of the food container, theagricultural/horticultural container, the blister package and thepress-through package are not particularly limited, but the sheet ispreferably drawn to a depth of not less than 2 mm for containing foodstuff, articles, and pharmaceutical products or the like. Thethicknesses of the containers are not particularly limited, butpreferably not less than 50 μm more preferably 150 to 500 μm, inconsideration of strength. Specific examples of the food containerinclude trays for perishable food, containers for instant food,containers for fast food and containers for a lunch box. Specificexamples of the agricultural/horticultural container include seedlingpots. Specific examples of the blister package include containers forpackaging foods. Other examples of the package include packages forvarious articles such as stationery, toys and dry batteries.

Other examples of the molded bodies produced using the resin compositionof the present invention include tableware such as dishes, bowls, pots,chopsticks, spoons, forks and knives; fluid containers; container caps;stationery such as rulers, writing utensils, clear cases and CD cases;daily commodities such as sink strainers, wastebaskets, washbowls,toothbrushes, hair combs and dress hangers; agricultural/horticulturalmaterials such as flower pots and seedling pots; toys such as plasticmodels; electrical appliance resin components such as air conditionerpanels and housings; and automotive resin components such as bumpers,interior panels and door trims. The shape of the fluid container is notparticularly limited, but the fluid container preferably has a depth ofnot less than 20 mm for containing a fluid. The wall thickness of thecontainer is not particularly limited, but is not less than 0.1 mm,preferably 0.1 to 5 mm, in view of strength. Specific examples of thefluid container include drinking cups and bottles for dairy products,soft drinks and alcoholic beverages; temporary storage containers forcondiments such as soy source, Worcester source, mayonnaise, ketchup andcooking oil; containers for shampoo and rinse agents; containers forcosmetics; and containers for agricultural chemicals.

The molded body made of the resin composition of the present inventionis subjected to a heat treatment to accelerate the crystallization ofthe molded body and thereby the heat resistance can be also enhanced.The heat treatment temperature is usually not less than Tg and not morethan Tm.

The resin composition of the present invention can be also made offibers. Although the producing method is not particularly limited, amethod for melt spinning and drawing is preferable. The melt spinningtemperature is preferably 160° C. to 260° C. If the melt spinningtemperature is less than 160° C., the melting extrusion tends to bedifficult. On the other hand, when the melt spinning temperature is morethan 260° C., the resin composition is remarkably decomposed, andthereby fibers having high strength tend to be hardly obtained. Themelt-spun fiber thread line may be drawn at a temperature of not lessthan Tg so as to be set to the intended fiber diameter. The obtainedfibers are used as fibers for clothing, fibers for industrial materials,and fibers for short fiber nonwoven or the like.

The resin composition of the present invention can be also developed tofilament nonwoven fabric. Although the producing method is notparticularly limited, examples thereof include a method for forming theresin composition into fibers by a high speed fiber spinning method,depositing and webbing the fibers, and making the web into fabrics usingheat pressure bonding method or the like.

EXAMPLES

The present invention will hereinafter be described more specifically byway of examples thereof. However, the present invention is not limitedto the following examples.

[Measuring Method or the Like]

Measuring methods or the like used for evaluating the following examplesand comparative examples are as follows.

(1) Flexural Strength:

A resin composition was injection-molded to obtain a molded piece of 150mm×13 mm×3 mm. The molded piece was subjected to an annealing treatment,and was used as a sample. The flexural strength was measured inconformity with ASTM-D790 by applying a load at a deformation rate of 1mm/min. The production conditions of the molded pieces are as follows.

Injection Molding Condition:

By means of an injection molding machine (IS-80G manufactured by ToshibaMachine), a cylinder temperature, a metal mold temperature, an injectionpressure, an injection time, a cooling time and an interval arerespectively set to 190 to 170° C., 15° C., 60%, 20 seconds, 20 secondsand 2 seconds. As the metal mold, a metal mold for ⅛ inch three-pointbending dumbbell test piece of ASTM standard was used.

Annealing Treatment Condition:

The molded pieces were heated for 30 minutes in an oven of 120° C.

(2) Hydrolysis Resistance Evaluation

Samples subjected to an injection molding and an annealing treatment inthe same manner as in the item (1) were stored at 60° C. and at arelative humidity of 95% for 300 hours and 500 hours using athermo-hygrostat (trade name: IG400, manufactured by Yamato ScientificCo., Ltd.). The flexural strengths were then measured in the same manneras in the item (1), and the strength-retaining rates were calculated toevaluate hydrolysis resistance.

The strength-retaining rate (%) was calculated as (strength-retainingrate)=(strength after being stored)/(strength before being stored)×100.

(3) Yellowness (YI Value):

A color-difference meter Z-Σ90 manufactured by Nippon DensyokuIndustries, Co. was used. A glass cell having a diameter of 30 mm and alength of 12 mm was filled with pellets each having a height of 3 mm, awidth of 3 mm and a thickness of 1.5 mm to measure the yellowness.

(4) Appearance:

Visual evaluation was performed. The appearance having no change wasevaluated as “very good”. The appearance having some blanching occurredbut having no deposit of metal salts and low-molecular weight substanceswas evaluated as “good”; and the appearance having the deposited metalsalts and low-molecular weight substances was evaluated as “poor”.

(5) Oxygen Permeability Coefficient:

A sheet-shaped sample (thickness: 200 to 300 μm) was produced byinserting resin composition pellets with a pair of aluminum plates,heat-pressing the pellets at 190° C. for 150 seconds, and cold-pressingthe heat-pressed article at 25° C. for 20 seconds. A measuring samplewas prepared by previously humidity-controlling the sheet-shaped sampleat 20° C. and at a relative humidity of 90% for 24 hours. The oxygenpermeability of this measuring sample was measured by a differentialpressure method using a differential pressure gas permeability meter(GTR-30XAU type manufactured by Yanaco). The oxygen permeabilitycoefficient (ml·mm/m²·day·MPa) was calculated by

(oxygen permeability coefficient)=(oxygen permeability)×(samplethickness).

The value of the oxygen permeability coefficient was an indicator of gasbarrier property. The smaller this value is, the more excellent the gasbarrier property is.

[Raw Materials]

Various raw materials used in the following examples and comparativeexamples are shown.

(1) Biodegradable Resin

Resin A: polylactic acid (trade name: Nature Works manufactured byCargill Dow, weight average molecular weight (MW): 190,000, meltingpoint: 170° C.)

Resin B: terephthalic acid/adipic acid/1,4-butanediol copolymer (tradename: Ecoflex manufactured by BASF, melting point: 108° C., melt flowrate (MFR): 5 g/10 minutes (190° C., load: 2.16 kg))

(2) Carbodiimide Compound

CDI: N,N′-di-2,6-diisopropylphenylcarbodiimide (trade name: Stabaksol Imanufactured by SUMIKA BAYER URETHANE CO., LTD.)

(3) Phosphite Organic Compound

PEP-36:bis(2,6-di-tert-butyl-4-methylphenyl)-pentaerythritol-di-phosphite(trade name: Adeka Stub PEP36 manufactured by ASAHI DENKA CO., LTD.)

JPH3800: hydrogenated bisphenol A·pentaerythritol phosphite polymer(trade name: JPH3800 manufactured by JOHOKU CHEMICAL CO., LTD.)

2112: tris(2,4-di-tert-butylphenylphosphite) (trade name: Adeka Stub2112 manufactured by ASAHI DENKA CO., LTD.)

(4) Hindered Phenol Compound

AO-330:1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene(trade name: Adeka Stub AO-330 manufactured by ASAHI DENKA CO., LTD.)

XL-1:2,2-oxamidobis-[ethyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate](trade name: Naugard XL-1 manufactured by Crompton-Uniroyal Chemical)

(5) Benzotriazole Compound

T-234: 2-(2H-benzotriazole-2-yl)-4-6-bis(1-methyl-1-phenylethyl)phenol(trade name: TINUVIN234 manufactured by Ciba Speciality Chemicals, Inc.)

T-326: 2-(2′-hydroxy-3′-t-butyl-5′-methylphenyl)-5-chlorobenzotriazole(trade name: TINUVIN326 manufactured by Ciba Speciality Chemicals, Inc.)

(6) Triazine Compound

UV-1164:2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl]-5-(octyloxy)phenol(trade name: UV-1164 manufactured by Cytec Industries)

(7) Hindered Amine Compound

CHIMASSOR:poly[{6-(1,1,3,3-tetra-methylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)imino}](trade name: CHIMASSORB944FDL manufactured by Ciba Speciality Chemicals,Inc.)

(8) Layered Silicate

MEE: A swellable synthetic fluoromica having dihydroxyethylmethyldodecylammonium ions between layers thereof (trade name: SOMASIF MEEmanufactured by CO-OP CHEMICAL CO., LTD., average particle diameter: 6.2μm)

MTE: A swellable synthetic fluoromica having methytrioctyl ammonium ionsbetween layers thereof (trade name: SOMASIF MTE manufactured by CO-OPCHEMICAL CO., LTD., average particle diameter: 6.2 μm)

[Production of Resin]

A PCM-30 type twin screw extruder manufactured by IKEGAI CORPORATION wasused for melt-kneading. The screw diameter was 30 mm, and the averagegroove depth was 2.5 mm.

Example 1

100 parts by mass of a resin A, 2 parts by mass of CDI, 4 parts by massof MEE and 0.5 parts by mass of PEP 36 were dry-blended, melt-mixed at190° C. under conditions of the rotation speed (rps) of the screw of 200rpm (=3.3 rps) and the retention time of 1.6 minutes, extruded,processed into a pellet shape, and dried to obtain a resin composition.The evaluation results of the physical properties and hydrolysisresistance of the obtained composition are shown in Table 1.

Examples 2 to 22 and Comparative Examples 1 to 11

Components and blending rate thereof each of examples and comparativeexamples were changed as shown in Table 1. Otherwise, in the same manneras in Example 1, compositions were obtained. The evaluation results ofthe physical properties and hydrolysis resistance of the obtainedcompositions are shown in Table 1.

In example 21 and comparative example 10, 90 parts by mass of a resin Aand 10 parts by mass of a resin B of a pellet-shaped were dry-blendedand used before the resins A, B were supplied to an extruder.

TABLE 1 Main resin composition (amount shows part by mass) BiodegradableCarbodiimide Phosphite organic resin compound Layered silicate compoundOther additives Type Amount Type Amount Type Amount Type Amount TypeAmount Examples 1 A 100 CD I 2 MEE 4 PEP36 0.5 2 A 100 CD I 2 MEE 4PEP36 1 3 A 100 CD I 2 MEE 4 PEP36 2 4 A 100 CD I 2 MEE 4 PEP36 0.1 5 A100 CD I 2 MEE 0.5 PEP36 0.5 6 A 100 CD I 2 MEE 2 PEP36 0.5 7 A 100 CD I2 MEE 8 PEP36 1 8 A 100 CD I 0.5 MEE 4 PEP36 0.5 9 A 100 CD I 4 MEE 4PEP36 0.5 10 A 100 CD I 2 MEE 4 JPH3800 0.1 11 A 100 CD I 2 MEE 4JPH3800 0.5 12 A 100 CD I 2 MEE 4 JPH3800 1 13 A 100 CD I 2 MEE 4 PEP360.5 AO-330 0.5 14 A 100 CD I 2 MEE 4 PEP36 1 AO-330 1 15 A 100 CD I 2MEE 4 PEP36 0.5 T-234 0.5 16 A 100 CD I 2 MEE 4 PEP36 0.5 UV1164 0.5 17A 100 CD I 2 MEE 4 PEP36 0.5 AO-330/XL-1 Each of 0.25 18 A 100 CD I 2MEE 4 2112 0.5 AO-330 0.5 19 A 100 CD I 2 MEE 4 JPH3800 0.5 AO-330 0.520 A 100 CD I 2 MTE 4 PEP36 0.5 AO-330 0.5 21 A/B 90/10 CD I 2 MEE 4PEP36 0.5 AO-330 0.5 22 A 100 CD I 2 MEE 4 PEP36 0.5 CHIMASSOR 0.5Comparative 1 A 100 examples 2 A 100 CD I 2 3 A 100 MEE 4 4 A 100 CD I 2MEE 4 5 A 100 MEE 4 PEP36 0.5 6 A 100 CD I 2 MEE 4 AO-330 0.5 7 A 100 CDI 2 MEE 4 T-326 0.5 8 A 100 CD I 2 MEE 4 UV1164 0.5 9 A 100 CD I 2 MTE 410 A/B 90/10 CD I 2 MEE 4 11 A 100 CD I 2 MEE 4 CHIMASSOR 0.5Characteristics of molded body made of resin composition Hydrolysisresistance Oxygen evaluation permeability (60° C., 95% RH, 300 hours)Appearance evaluation Color Flexural coefficient Flexural strength (60°C., 95% RH, 500 hours) tone strength ml · mm/m² · Retaining Flexuralstrength Appearance YI MPa day · MPa MPa rate (%) MPa evaluationExamples 1 21 108.9 122 84.0 65.2 33.0 Good 2 11 119.6 110 104.2 87.189.6 Very good 3 7 125.0 130 98.1 78.5 85.3 Very good 4 23 113.4 10573.5 64.8 31.2 Good 5 15 110.5 150 90.3 81.7 65.2 Very good 6 18 98.5140 75.5 76.6 74.5 Very good 7 17 105.1 57 80.1 76.2 58.0 Very good 8 20110.2 98 70.1 63.6 35.2 Good 9 19 102.5 89 88.0 85.9 80.6 Very good 1021 110.1 105 76.0 69.0 55.0 Good 11 13 122.1 121 115.2 94.3 108.3 Verygood 12 7 128.5 133 121.0 94.2 110.5 Very good 13 10 110.5 98 92.1 83.389.6 Very good 14 9 116.8 97 105.3 90.2 84.9 Very good 15 12 101.6 10583.6 82.3 70.4 Very good 16 13 106.0 95 83.5 78.8 71.3 Very good 17 12106.7 93 88.5 82.9 75.5 Very good 18 17 101.7 98 64.5 63.4 28.5 Good 1912 105.4 102 93.2 88.4 88.5 Very good 20 15 102.3 145 78.1 76.3 35.1Good 21 14 104.7 118 82.5 78.8 32.3 Good 22 16 102.1 101 80.7 79.0 62.1Good Comparative 1 15 135.4 200 39.2 29.0 0.6 Poor examples 2 10 111.7200 86.0 77.0 Incapable Poor measurement 3 44 105.8 103 8.0 7.6Incapable Poor measurement 4 34 109.1 98 56.9 52.2 21.1 Poor 5 16 97.595 10.5 10.8 Incapable Poor measurement 6 17 106.0 88 62.4 58.9Incapable Poor measurement 7 40 98.8 100 50.8 51.4 Incapable Poormeasurement 8 29 106.3 115 57.4 54.0 18.3 Poor 9 27 95.4 140 38.3 40.1Incapable Poor measurement 10 35 102.2 135 11.5 11.3 Incapable Poormeasurement 11 42 109.5 98 42.5 38.8 Incapable Poor measurement A:Polylactic acid B: Terephthalic acid/adipic acid/1,4-butanediolcopolymer CD I: N,N′-di-2,6-diisopropylphenylcarbodiimide MEE: SOMASIFMEE MTE: SOMASIF MTE PEP-36:Bis(2,6-di-tert-butyl-4-methylphenyl)-pentaerythritol-di-phosphiteJPH3800: Hydrogenated bisphenol A•pentaerythritol phosphite polymerAO-330:1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzeneXL-1:2,2-oxamidebis-[ethyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]T-234: 2-(2H-benzotriazole-2-yl)-4-6-bis(1-methyl-1-phenylethyl)phenolUV-1164:2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl]-5-(octyloxy)phenolT-326: 2-(2′-hydroxy-3′-t-butyl-5′-methylphenyl)-5-chlorobenzotriazoleCHIMASSOR:Poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)imino}]

In each of the resin compositions of examples 1 to 22, the retainingrate of the flexural strength of not less than 60% was maintained, andthe test pieces after moisture heat test had a surface on whichlow-molecular weight substances or metal salts were not deposited, andhad superior appearance. Since each of the resin compositions containedthe layered silicate, the resin composition had low oxygen permeabilitycoefficient. Although the resin composition contained the layeredsilicate, the resin composition had a low YI value.

In examples 13 to 22, the same hydrolysis resistance effect as that ofthe case using only the phosphite was obtained by using the phosphitecompound along with the other additive by the clear comparison ofexamples 13 to 22 and systems using only the additive other than thephosphite compound as shown in comparative examples 6 to 8, 11.

On the other hand, each of comparative examples had the followingproblems. Since the resin compositions of comparative examples 1, 2 didnot contain the layered silicate, the resin compositions had low gasbarrier property. Since the resin compositions of comparative examples1,2 did not contain the phosphite compound, the resin compositions hadinferior hydrolysis resistance. Since the resin composition ofcomparative example 3 had excellent gas barrier property, but containedneither the carbodiimide compound nor the phosphite compound, the resincomposition had inferior color tone, and had insufficient hydrolysisresistance and appearance. Since the resin composition of comparativeexample 5 did not contain the carbodiimide compound, the hydrolysisresistance of the resin composition did not reach an aimed level. Sincethe resin compositions of comparative examples 4, 6 to 11 did notcontain the phosphite compound, the resin compositions had insufficient,hydrolysis resistance and appearance, and the resin compositions otherthan that of comparative example 6 had insufficient color tone.

1. A biodegradable resin composition comprising: 100 parts by mass of abiodegradable polyester resin comprising not less than 50% by mass ofpolylactic acid; 0.1 to 5 parts by mass of a carbodiimide compound; 0.1to 10 parts by mass of a layered silicate; and 0.01 to 5 parts by massof a phosphite organic compound.
 2. The biodegradable resin compositionaccording to claim 1, wherein the biodegradable resin composition has astrength-retaining rate of not less than 60% when being held at 60° C.and at a relative humidity of 95 % for 300 hours.
 3. The biodegradableresin composition according to claim 1, wherein the biodegradable resincomposition has a YI value of not more than 25 as measured by acolorimeter.
 4. The biodegradable resin composition according to claim1, wherein the layered silicate comprises primary, secondary, tertiaryor quaternary ammonium ions, pyridinium ions, imidazolium ions orphosphonium ions ionically bonded between layers thereof.
 5. Abiodegradable resin composition comprising: 100 parts by mass of abiodegradable polyester resin comprising not less than 50% by mass ofpolylactic acid; 0.1 to 5 parts by mass of a carbodiimide compound; 0.1to 10 parts by mass of a layered silicate; a phosphite organic compound;and at least one additive selected from the group consisting of ahindered phenol compound, a benzotriazole compound, a triazine compoundand a hindered amine compound, wherein the biodegradable resincomposition comprises the phosphite organic compound and the additive inan amount of 0.01 to 5 parts by mass in total.
 6. The biodegradableresin composition according to claim 5, wherein the biodegradable resincomposition has a strength-retaining rate of not less than 60% whenbeing held at 60° C. and at a relative humidity of 95 % for 300 hours.7. The biodegradable resin composition according to claim 5, wherein thebiodegradable resin composition has a YI value of not more than 25 asmeasured by a colorimeter.
 8. The biodegradable resin compositionaccording to claim 5, wherein the layered silicate contains primary,secondary, tertiary or quaternary ammonium ions, pyridinium ions,imidazolium ions or phosphonium ions ionically bonded between layersthereof.
 9. A molded body comprising the biodegradable resin compositionaccording to claim
 1. 10. A method for producing a biodegradable resincomposition comprising: adding a layered silicate when melt-mixing thebiodegradable resin composition or when polymerizing the biodegradablepolyester resin, in producing the biodegradable resin compositionaccording to claim
 1. 11. A method for producing a biodegradable resincomposition comprising: adding a carbodiimide compound and a phosphitecompound when melt-mixing the biodegradable resin composition or whenpolymerizing the biodegradable polyester resin, in producing thebiodegradable resin composition according to claim
 1. 12. A molded bodycomprising the biodegradable resin composition according to claim
 5. 13.A method for producing a biodegradable resin composition comprising:adding a layered silicate when melt-mixing the biodegradable resincomposition or when polymerizing the biodegradable polyester resin, inproducing the biodegradable resin composition according to claim
 5. 14.A method for producing a biodegradable resin composition comprising:adding a carbodiimide compound and a phosphite compound when melt-mixingthe biodegradable resin composition or when polymerizing thebiodegradable polyester resin, in producing the biodegradable resincomposition according to claim 5.